Neither does the South, except for its maniacal attachment to slavery.
There's also the Indian issue, which can cause problems for the South more than the North. Imagine a scenario where President Clay, or more likely President Adams Jr, tries to enforce Cherokee land rights in Georgia.
Anyways, the demographic and economic success of the "North" matter because the land rush north of the Ohio River can be characterized as a race between Yankees and Butternuts which the Yankees "won". This was pivotal in the Old Northwest's long-term preference for the "North" once these states entered the Union. And for the OP's scenario, it seems much more likely if New England feels isolated from the rest of the country.
The Treaty of Ghent is the last realistic time before which this process can be reversed or at least slowed down.
And then there's the west (of the Mississippi) part of it.
The demographic and economic success of the "North" would require "the North" to represent something where Ohio and Massachusetts see each other as fellow "Northerners" in the same way Louisiana and Virginia are fellow Southern states.
When and where did the Old Northwest ever identify itself like that? The fact that the "North" was all pro-Union in the actual ACW isn't the same thing.
Because it the demographic surge from New England into the Old Northwest and the economic ties after the development of the steamboat, canal and railroad that pulled the Old Northwest to the eastern seaboard part of the "North" rather than the South. Before Ghent, these ties aren't inevitable, so a Civil War with a part of the "North" breaking apart is much more likely. Although if the Northwest Ordinance gets suspended then perhaps this inevitability can be altered, although similarly I don't see that happening after 1815.